Floating platforms are being considered as economic solution to support offshore wind turbines in deep sea to harness wind energy. The hydrodynamic interaction of such platforms with ocean waves and the understanding and quantification of the non linearity involved in these interactions are of vital importance while designing a cost effective and durable floating platform. This paper examines the importance of these non-linear interaction components for a TLP-type floating platform. Non-linear equations for motions and forces are formulated and solved and the results are obtained to demonstrate the significance of the nonlinear wave force components. A limited comparison with experimental data is also presented to show the acceptable accuracy.

INTRODUCTION

Wind is the world''s fastest growing renewable energy source and has become an integrated part of the modern power production in many countries. This trend is expected to continue with falling costs of wind energy and the urgent international need to tackle CO2 emissions to prevent climate change. Future development of onshore wind farms are hampered by concerns about turbine noise, aesthetic (visual) impact and scarcity of land for turbine placement near major population (and energy load) centers where energy cost and demand is high. Locating wind turbines offshore alleviates these concerns and also offers advantages such as higher and steadier wind speed, and availability of larger area sites than onshore. In offshore areas having deeper water depth, the fixed offshore wind power structure installation practice of driving piles into the seabed becomes economically infeasible. Therefore it is strongly desired to develop a cost effective floating platform to support wind turbines. Several concepts of floating offshore wind turbines were studied and some of them are under research. The examples include MUFOW by Baltrop (1993), toroidal shape floater by Bertachhi et.al (1994), FLOAT study by Tong (1998), Tri-floater by Delft University (2002) and MIT/NREL TLP by Sclavounos et al (2007).